1. Field of the Invention
The invention relates to the field of electrical devices and in particular to a discrete device in which the design and structure of a transformer/inductor and capacitor are integrated.
2. Description of the Prior Art
A continuing and permanent trend in the electronics industry is to increase the packaging density in order to reduce the size of products. This has been realized not only through the use of integrated circuits wherever possible or a custom large scale integration of semiconductor circuits, but also in the miniaturization of discrete electrical devices which do not lend themselves to semiconductor integrated technology.
Miniaturization of device size typically results not only in a higher utility of the resulting product, but often in a reduced cost of materials and manufacturing.
The kinds of discrete electronic products which have been integrated with only partial success specifically include transformers or inductors and capacitors. For example, integration of a capacitor with an inductor has been achieved in integrated devices using amorphous metal ribbons.
ALLEY et al., "Amorphous Metal Lamp Ballast Having a Capacitor Integral with the Magnetic Core", U.S. Pat. No. 4,211,957 (1980), shows a magnetic core of lamp ballast which is bifilar wound from a thin amorphous metal strip and wherein the laminations of the magnetic circuit are also used as the plates of a capacitor.
CARR, "Self Resonant Ignition Coil and System", U.S. Pat. No. 3,566,202 (1971), shows an inductive ignition coil which includes a built-in capacitance used to resonate the secondary of the coil.
BJOERKLUND, "Unitary Magnetic Core and Condenser", U.S. Pat. No. 2,524,754 (1950), also describes a ballast for an electric discharge lamp in which a capacitive unit is built up of coils of magnetic material electrically insulated from each other and forming the electrodes of a condenser while the inductive unit is wound upon the condenser.
Thus, it was well understood in the prior art to devise various types of integrated units which act both as an inductor and capacitor by appropriate exploitation of a metallic would surface of coil to act both as part of the inductor coils and the conducting plates of the capacitor. Typically, amorphous metal was used as the material for the structure performing this dual function. However, in such prior art units the inductive and capacitive values obtained in such integrated structures are limited in range.
Therefore, what is needed is some type of design for an integrated transformer/inductor and capacitance device wherein the inductive and capactive range of the device may be substantially increased without sacrificing any of the miniaturization achieved by virtue of the integration.